The present invention relates to support structure for a shoe and, more particularly, to a bladder arrangement comprising fluid filled chambers having support pillars that provides additional stability to the shoe.
The human foot and leg endures a great deal of stress, even during the performance of simple activities like walking. More rigorous activities, such as running and jumping, subject a person""s feet and legs to even greater stress. This is particularly true of athletes, many of whom perform such rigorous activities on a daily basis.
In order to alleviate the unusually high levels of stress imparted on an athlete""s feet and legs, athletic shoes are typically designed to absorb the force of impact associated with running and jumping. Specifically, athletic shoes often include supporting and cushioning structures to absorb these forces of impact. These supporting and cushioning structures are typically positioned in the rear foot or heel section of the shoe where the forces of impact are most likely to be experienced. Many athletic shoes also provide supporting and cushioning structures on the sides of the shoe, not merely in the region of the heel. These supporting and cushioning side structures absorb the force of impact along the sides of the athlete""s foot.
Currently, there are many configurations for these supporting and cushioning structures. Some of these configurations include the use of fluid-filled chambers. A fluid-filled chamber typically comprises a fluid-filled chamber or pocket located in the sole of an athletic shoe. The fluid may be air or else any other type of gas or liquid that is deemed to provide the desired level of stability. Depending on the amount of support desired, the fluid-filled chambers may be maintained at the ambient pressure, may be pressurized beyond the ambient pressure level, or else may be de-pressurized below the ambient pressure level.
U.S. Pat. No. 5,575,088 discloses a fluid-filled bladder arrangement imparting cushioning to a heel section of a shoe. The bladder arrangement includes individual, concentric chambers that are connected so as to allow fluid to be communicated between the chambers. The concentric chambers are ring-shaped with the inner ring having a lower height than the outer ring. The arrangement forms a cradle for the heel, providing support and stabilization therefor. The pressure within the chambers of the bladder is uniform because fluid pressure is equalized between the ring sections, which are in fluid communication with one another.
U.S. Pat. No. 5,353,459 to Potter et al. discloses a bladder arrangement in which separate chambers are maintained at different pressures through the use of distinct interconnecting tubes. Specifically, Potter discloses a bladder arrangement having tube-shaped chambers that are disposed at and form the lateral and medial sides of the bladder, a rear central chamber disposed between these tube-shaped chambers at one end thereof, and a front central chamber disposed between these tube-shaped chambers at another end thereof. When disposed within a shoe, the rear central chamber of the bladder arrangement provides support to the heel of the wearer, the front central chamber provides support to the middle of the wearer""s foot, and the two tube-shaped chambers provide support to the medial and lateral sides of the wearer""s foot.
One problem that is experienced by the use of fluid-filled chambers as supporting and cushioning structures in shoes is that, due to their compressibility, the fluid-filled chambers may not provide the desired amount of support and stability. For example, in addition to the impact forces that are experienced by the feet and legs of an athlete, many sports require an athlete to rapidly change his or her direction of motion. Still other sports require an athlete to place his or her foot on a field or playing surface which is not perfectly flat. Both of these situations may result in the athlete""s foot undesirably rotating relative to the athlete""s leg. This may result in the athlete performing inadequately, e.g., failing to execute a desired movement. In addition, if the athlete""s foot rotates too far relative to the athlete""s leg, the athlete may suffer an injury. For instance, if the inner (e.g., medial) side of the foot is rotated downwardly too far relative to the outer (e.g., lateral) side of the foot, the foot may be over-pronated and an injury may occur. Likewise, if the medial side of the foot is rotated upwardly too far relative to the lateral side of the foot, the foot may be over-supinated and an injury may also occur. Of course, these are merely two types of excessive rotations that can cause foot injuries.
Thus, while fluid-filled chambers may provide adequate protection against impact forces, they may not provide adequate stability if they deform too much when they are compressed. For instance, even though a fluid-filled chamber may be pressurized, the fluid-filled chamber may not be able to provide an adequate amount of support to stabilize the foot of a large athlete. In addition, the fluid-filled chamber may not be able to provide an adequate amount of support to stabilize the foot of an athlete that participates in a sport that requires rapid changes in direction, e.g., basketball, even if it is able to provide an adequate amount of support to stabilize the foot of an athlete that participates in a sport that does not require these movements, e.g., marathon running. If the amount of support provided by the fluid-filled chamber is inadequate, the athlete may not receive the support need to perform optimally, or else may risk injury when the athlete""s foot undesirably rotates relative to the athlete""s leg.
The present invention, in accordance with one embodiment thereof, relates to a support structure for a shoe. The support structure comprises a bladder arrangement including at least one (and preferably two) fluid-filled chamber arranged in a sole of the shoe. The fluid-filled chamber has outer walls with a fluid disposed therein. Preferably, the fluid is pressurized. The fluid-filled chamber is configured to be compressively deformed when an external pressure is applied thereto, such as the pressure exerted by a wearer""s foot.
The support structure also includes at least one pillar disposed in the fluid-filled chamber. The pillars are configured to decrease the amount by which the fluid-filled chamber is compressively deformed when the external pressure is applied thereto. Preferably, the pillars are configured such that, although they decrease the amount by which the fluid-filled chamber is compressively deformed when the external pressure is applied thereto, they do permit the fluid-filled chambers to be deformed sufficiently to provide adequate protection against the force of impact during use. Advantageously, the pillar has a tapered shape, such that it tapers from a first, e.g., larger, dimension at its connection to the outer walls of the fluid-filled chamber to a second, e.g., smaller, dimension at a point between the outer walls of the fluid-filled chamber, so as to provide a desirable amount of structural rigidity.
In a preferred embodiment, the bladder arrangement of the support structure includes two fluid-filled chambers, each of which are positioned along a medial side and a lateral side of the heel region of the shoe. The fluid-filled chambers are preferably encapsulated by a cushioning material such as polyurethane foam.